The Soviet Union and Yugoslavia disappeared from the world map decades ago, but the political divisions, disputed borders and competing national ambitions left behind by their collapse continue to influence international relations.

Their breakups created independent countries, redrew borders and changed the balance of power across Europe and Central Asia. In some places, independence came with relatively little violence. In others, the collapse of a shared state triggered wars whose consequences remain unresolved.

The Soviet Union: 15 countries from one superpower

On December 26, 1991, the Soviet Union formally ceased to exist, ending the life of a superpower that had shaped global politics throughout the Cold War.

The union, which comprised 15 republics, broke apart after years of economic difficulties, political reforms, rising nationalist movements and growing opposition to central rule in Moscow.

Its dissolution produced 15 independent states, including Russia, Ukraine, Belarus, Georgia, Armenia, Azerbaijan and the three Baltic states of Estonia, Latvia and Lithuania.

Russia emerged as the Soviet Union’s principal successor state, inheriting its permanent seat on the United Nations Security Council, much of its foreign assets and responsibility for its outstanding debt.

The division, however, did not settle every question of territory, identity and political allegiance.

Ukraine became an independent country, but its relationship with Russia remained a source of tension. Russia’s annexation of Crimea in 2014 and its full-scale invasion of Ukraine in February 2022 brought the unresolved consequences of the Soviet collapse into a devastating new phase.

The conflict has also intensified disputes over national sovereignty, the security of former Soviet republics and the boundaries of Russian influence in Eastern Europe.

Other parts of the former Soviet Union experienced their own territorial conflicts. Disputes involving Armenia and Azerbaijan over Nagorno-Karabakh, as well as conflicts affecting Georgia and Moldova, demonstrated how the collapse of a central authority could leave behind competing claims over land and political control.

Yugoslavia: a breakup marked by war

Yugoslavia’s disintegration in the early 1990s followed a different path, with nationalist politics, economic crisis and deepening disagreements between its constituent republics contributing to the collapse of the federation.

The country had brought together six republics: Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia and Slovenia. Kosovo and Vojvodina were autonomous provinces within Serbia.

After the death of longtime leader Josip Broz Tito in 1980, the federal system struggled to contain competing political and national ambitions. As communist rule weakened across Eastern Europe, calls for independence grew.

Slovenia and Croatia declared independence in June 1991. Macedonia and Bosnia and Herzegovina followed, while Serbia and Montenegro initially remained together in a new federal state.

The breakup was accompanied by wars in Croatia and Bosnia and Herzegovina, with civilians suffering mass displacement, atrocities and widespread destruction. The Bosnian war ended with the 1995 Dayton peace agreement, which established a political framework that continues to shape Bosnia and Herzegovina’s government.

Kosovo became another major source of international tension. After years of conflict, it declared independence from Serbia in 2008. The United States and many European countries recognised Kosovo, but Serbia continues to reject its independence, and the international community remains divided over its status.

Montenegro separated from its union with Serbia in 2006, completing another stage in the dissolution of the former Yugoslav state.

Today, disputes over Kosovo, political divisions in Bosnia and Herzegovina and competing interpretations of the wars continue to affect relations across the Western Balkans.

Czechoslovakia: a different ending

Not every country that disappeared left behind a major armed conflict.

Czechoslovakia separated peacefully into the Czech Republic and Slovakia on January 1, 1993, following negotiations between their political leaders.

Often called the Velvet Divorce, the separation showed that the dissolution of a multinational state could produce two independent countries without a war.

The contrast with Yugoslavia highlights the importance of political negotiations, institutional arrangements and the willingness of competing leaderships to accept an agreed settlement.

The disappearance of a state does not automatically resolve disagreements about its territory, resources, debts or national identity.

Newly independent countries must establish institutions, protect their borders and determine their relationships with neighbouring powers. Former ruling states may also seek to preserve influence over territories they once controlled, creating friction when their ambitions conflict with the sovereignty of successor countries.

The Soviet and Yugoslav experiences demonstrate how the collapse of a political system can create opportunities for independence while leaving difficult questions for future generations.

Those questions remain visible today in the war between Russia and Ukraine, Serbia’s dispute with Kosovo and the fragile political arrangements governing Bosnia and Herzegovina.

The flags and governments of the Soviet Union and Yugoslavia are gone, but the borders established during their collapse remain central to some of Europe’s most consequential political and security disputes.